Method of electric resistance welding a laminated sheet metal structure



.Fully 27, i948. M PAR-[10T 2,445,861

METHOD 0F ELECTRIC RESISTANCE WELDING LAMINATED SHEET METAL STRUCTURESFiled Aug. 6, 1942 2 Sheets-Sheet 1 l VENTOR ATTORNEYJ.

July 27, 1948. M, PARTlQT 2,445,801

METHOD OF ELECTRIC RESISTANCE WELDING LAMINATED SHEET METAL. STRUCTURESFiled Aug. 6, 1942 2 Sheets-Sheet 2 Irl/1 w Z3 V 3,21 R20 ASL i BYAare/cf ,Mr/0r M3141. @aww Patented July 27, 1948 UNI;

lvmrHoD'oEfEIEGTRIC RESISTANCE WE'D# INGALAMINATED SHEETf'METAL STRUG-Maurice Partiqtfloroton, Comu-,- assignortolhe .Y

Nitralloy Corporatiom a .fcornoratiomot Dolan Waffe Application-hunnen,194affserie1 Namaste e (o1.Y .aree-1m.,

1 2 This.inventomrelatesetoftanimprovedn ethod of; electriei resistance.wel-.cling a -.filaminated,.fsheet metals' structureWhereinfthawelds.betweenzeach adiacentpair; of: sheets are; disposed .in-spacednrelation. tovand out v.ort alignmentV withizthe.: fweldsjoiriirlgaieah sheet of `the -pair to Qthereadiaeen-.t sheets of. the.laminated structune.,f The .ini/.en tion may he applied in producing.laminatedsheet metal structures for;v various :purposesnbut .will be.idescribed. hereinafter wthqparticular -freierfg ence :tot themanufacture not-laminated structures adapted to` resist-' imnaotsandto.. distributefthe force oflocalizedirnpacts over a considerableareaff. the structurewithoutvbringns. about permaf nent deformation..l

The invention has lfor an object to, ,providerari improvedmethod ofmaking; a laminated sheet metalstructure in which-nthefvariouslaminaeare secured to each other.: in such .a Way that localized zonesof weaknessa largely ifmot L .completely eliminated .and the overallresiliency. othe; struee tureis considerably improved.

Another object of the invention is to :provideran improved methodtofassembling Aand welding gto gether the constituent .pa-rtsi oisuch. a.laminated sheet metal structure.l

Af still .further object `is .-to` Aprovide.mei-,limi- Whereby. a.laminatedysheet qmetal: structure @is built up Ybizz-welding. .aplurality of metalsheetsztoe gether` at, sparedA .points `With`lsligl'itly, :corrugated or bowed ,sectionsfbetweenithe :weldswhichiprorf vide. intersticest Still anotheriobject of imyinventionisito; `'proa vide a method whereby. it isma-de possilbletofpro-l duce a.huilt-upv y or laminated sheet metal .strue-i ture comprisingat leastthree sheets or-.relatively thin tplates joined together. `atspacedmointsfby Welding and Lin .which the,` welds; joining any.: twosheets together are. `in index staggered relationtgto thewelds joining,.any other two-.sheets .rof,--:the structure.

Other objects; of the-.invention will*` :beoomeap parent fromI thefiollowingedescription:

In accordance with the. present inventions@ have provided a method;ofiutilizing, thetelectribal resistance Welding V.process A"to.fform-.amlaminated sheet metal structure which i-isf made.: etv-.a.;pliJ-i rality .of i relatively -thin sheets. or plates fofxmetalin which the sheets .arersd assembiedand. .secured bywelding that noneof thezzonesrfor areas'wat which the. sheets. are. .seeured'tofeacheotherfiare inalignmentin .a direction fnorma1.to..the surface' of.the structure. Preferably 4.the sheets; aresise. curedto each." otherWiththeaweldsiarrangedeiir index spacedfrlelation. Byffindexispacedirelatlonf;

. 2 isfmeant; that thetveldsf-are .-so spaced apart that no two ormoreeofythemvare inalignmen-t ina direction. nor-malstol @the surface of.the assembled plate structure.

AceordingftoA one-advantageous and ,preferred modification". eithenduring-@the formation nof i the individual sheets orel darmer thewelding i operation,4 at leastycertain ,ofe the sheetsare ,bowedslightly between fthewelds -so that `they possess increased capacity-for Lspringing .under impacts and therebyfdissipate atleast a part ofYthe. energy of, the impactigas, lfor example;Y the impactfaprojectile-.when the structure -is used as armor plate. An additionalfeature of my invention consists in. so @controlling the 'depths' of thespaces betvteen,q they sheets; as4 ftd-insure that each -sheetoraplatefshall-bezfreeto uifidergov consderablerlexf ure under :impact-3ybutV at-.the zsameftime' will be brought z irl-toy;supportingrcontatwith the next succeeding sheet-beforewits elasticvglimit `isfex-`ceedc.1.d,.` i

For .a better'eunderstanding .ofV the invention, reference mayx be .hadto theaaceompanying -drawe ing in which:

Figure lv1 isvauviewi in verticalgcrosssection on the line v1-i.|;ofQFigure'Bi otra portionaofea v.lami-` natectA vsheet v4meta-lstructure r"during: thei process of! fassembly .illitstnating.saisonlthezlele'otrodes by meansI lof-f Whibh'thefsheetsiare Welded. together:

Figure 2 yis-a-topY plan view .of fa portinvof the laminated'fstruetureiillu'strating' the :manner inl-whiehlthe-wellslare disposed instaggered rela;V

tionto -eaeh `l'otl'ier i Figure# 3 isi 'a ViewI in part verticalsection and in- `part side'elevation df-#a modified.A form oda-mi'-nated-- structure *in-the process-of 'being assembled bya mo'diedmethodiof Welding the sheets together; y

Figure-4' is a view-in-sideelevation ofthe lamihated!struQtureiof-Figure3 afterfthe weldingA electrodes :and welding pressure "have been re.moved: 1 and.

Figure 5i's 'a viewn cross :sectionot another type vofwlaminated",structure formedjiby vthe w'eld-, ing method of 'the' presentinvention;l

As shown irrFig'ure` 1 of the drawings, the 111ethr-1dis.4 applied..to.the production of alam;- natedgstructure formed: of.`a.pluralitxtoislieetslof, steel ULI] l,tl\2',,.l.3and, lb't'vvhich arepre-.formed to. .render v them corrugated 'ont lines... extendingacross-the sheetsef When these: Sheets are Steked one-.upon the. f.othenV ,as :illustrated fin .-11, the resulting; estructura' twill 1;have @fa =;.generally: honeycombed cross-sectional shaple iwitl'ispacesbetween the sheets at certain zones and other portions of the sheets incontact with each other.

In order to assemble and weld the various sheets together, conventionaltypes of watercooled welding electrodes may be used in producing thewelded joints between the sheets I and II at the points indicated, forexample, by the letter "B. All of the welds B between the sheets II] andII may be in the same straight line extending, for example, laterally ofthe sheet, or they may be alternately at a small distance to the rightor left of the center line of the mandrels as shown in Figure 2.

In order to assemble the remaining sheets forming the laminatedstructure I resort to a novel method of controlled welding in order tospace the welds 4properly one from the other in index spaced relationand in order to exert the proper.

welding pressure on the sheets. It is well known that when spot weldingelectrodes of similar surface contact area are positioned in alignmenton opposite sides of a metal structure to be welded and a suitablecurrent flow is established, welds will be formed directly in alignmentwith the electrodes between each adjoining pair of sheets disposedbetween the electrodes. In order to avoid this action and to conne thewelds to an index staggered relation, I have provided an enlarged lowerelectrode plate I which rests upon the lower welding electrode I6 and isshaped to iit the contours of the lower sheet or fplate Ill. In this waythe electric current is distributed over a wide area of the lower sheetI0 and the adjacent sheet II.

In order to concentrate the electrical energy Within a more restrictedarea at the points where the welds lare to be formed between sheets I Iand I2 and to insure Ithat a proper welding pressure may be applied atthe weld zones, a mandrel Il, formed of copper or other highlyconductive metal, is placed between the sheets I0 and II. This mandrelsupports the sheet II so that a proper welding pressure can be appliedthereto; When the sheet I2 is placed upon the sheet II and the topelectrode IB is brought into contact with the sheet I2 in opposedrelation to the mandrel I1 and a Welding current is passed, the weld Cisformed in alignment with the tip of the electrode IB, but the metal isnot fused below the mandrel I'I because of the distribution of thecurrent throughout the area of the mandrel I'I. After one weld C hasbeen formed the electrodes and mandrel C may be shifted longitudinallyto form the next succeeding weld C or if desired a plurality of sets ofelectrodes IB and I8,` electrode plates I5 and mandrels I'I may -be usedsimultaneously to form all or a predetermined number of the welds C.

After the series of welds C have been formed and the sheet I2 has beensecured at all the desired spots to the sheet I I, the sheet I3 may thenbe placed on top of the sheet I2 and mandrels I1 placed in the properlocations between the sheets II and I2 to support the sheets anddistribute the current as described above. The electrodes I6 and I8 andthe electrode plates I5 then may be shifted relatively yto the welds Band C to positions that will insure that welds D between the sheets I2and I3 will lie in a different vertical plane than the welds B, referredto above, and as shown particularly in Figure 2 of the drawings. Thesheets I2 and I3 then are secured together by a series of welds D whichare spaced in staggered relation to and on different lines from any ofthe welds B and C.

If still another sheet I4 is to be assembled into the laminatedstructure a series of mandrels I'I Will .be inserted in the series ofenlarged spaces between the sheets I2 and I3. Preferably the mandrels inline therewith between the sheets Ill and I I will be allowed to remainin place so as to insure firm supports for the superposed mandrels andpermit of the application of a proper welding pressure. If desired, themandrels II positioned between sheets II and I2 may be permitted toremain in place during the welding of the sheet I4 to the sheet I3. Asis the case when preparing to form the welds D, the electrodes andelectrode plates'will be shifted laterally to insure that the welds Ebetween the sheets I3 and I4 will be staggered or out of line laterallywith the welds C between sheets II and I2.

The assembly of the various sheets can continue until the desiredthickness is built up in accordance with the requirements for theservice to which the laminated structure is to be put.

When the assembly is finished, the intermediary mandrels are removed andthe plate assembly may be pressed back to a total thickness which ispredetermined :by ballistic or other suitable impact tests to be thebest one for the intended service. In general the spacing of theindividual sheets or plates at the end of the pressing operation shouldbe such that each sheet may be considerably flexed on application ofpressure at a point on the surface thereof intermediate the weldsconnecting it with an adjacent sheet and yet such `portion of the sheetmay be forced into contact with such adjacent sheet before the elas-4tic limit of the metal making up such portion has been reached. Thedimensions of the mandrels will be so determined with respect to Itheinterstitial spaces that are to be retained in the final plate as tokeep as low as possible the stresses that are set up in the fiatteningstep. dt has been found that mandrels of a thickness and a width of 1%work very well for a spacing of about 5 inches between center lines ofthe welds when sheets of from .04" to .08" are being used to form thelaminated structure.

When relatively rigid sheets or plates are used, as for example, whenthey are more than 0.125 thick it will usually be more convenient tosubstitute, for the method above described and shown in Figure 1, themethod illustrated in Figures 3 and 4 wherein the laminated structuremay be formed from initially flat sheets or plates of metal and thesheets bowed slightly during the welding operation. As shown in Figure3, the laminated structure may be formed of four sheets of metal 20, 2I,22 and 23. In assembling these sheets, the sheets 20 and 2| may beplaced on top of each other and supported on a lower electrode 24 ofconsiderably greater area than the area of the upper electrode 25. Theelectrodes 24 and 25 preferably are watercooled and can be forcedtogether under high pressure so that during the welding operation deepdimples are formed in the surfaces of the sheets and the metal is forcedto iiow so that the sheets 20 and 2I are bowed between the welds. Inorder to secure Ithe remaining sheets 22 and 23 together and to thesheet 2I, the bottom electrode 24 may be provided with an insulatedportion 24a in alignment with the top electrode 25 and slightlydepressed with respect to the face of the electrode. The insulatedportion prevents current from passing in a straight line normal to thesurfaces of the sheets between the electrodes. With this arrangement aweld will be formed only at the point of contact of the two platesimmediately beneath and adjacent the electrode 25 as at 26 and not atthe place where the insulated portion 24a engages the sheet 20. Thepaths taken by the current in passing between the electrodes is shown bythe arrows in Figure 3. In this form of laminated structure the weldsare staggered as in the form shown in Figures 1 and 2 so that no two ofthese welds are in alignment normal to the surface of the plate. Whenemploying the method of Figure 3, it is advisable to increase the numberof welds by spacing them closer together and in this way insure asuciently low resistance to flow of current to permit of staggeredwelding instead of welding in a straight line. On release of the weldingpressure the sheets will lose some of the bowed shape between the weldsand assume a spacing such as shown in Figure 4. Interstitial spacingthat will leave a distance of from .02 to .06" between sheets may `beproduced with suitable regulation of the welding pressure and accordingto the thicknes of the sheets.

The welding operation can be facilitated further by providing relativelyrigid spacers between the sheets so that adequate welding pressures canbe obtained between the various sheets. As illustrated in Figure 5, thespacers may take the form of a sheet of Wire mesh 30 interposed betweeneach of the sheets 3|, 32 and 33. The pressure of the welding electrodesis resisted by the sheets and the wire mesh and welds 34 will be formedat the intersection of the Wires where they are disposed beneath thesmaller or upper welding electrode shown in Figures 1 and 3. If desired,the wire mesh 30 may be provided with metal disks 35 at the intersectionof certain of the wires and at the welding zones to fuse with the sheets3|, 32 and 33 and secure these sheets together. The welds will bestaggered in the manner herelnbefore described.

It will be understood that any desired number of sheets may .beassembled into the laminated sheet metal structure and the thickness ofthe individual sheets may be varied considerably.

It will be understood that considerable variations may be made withrespect to the shape of the sheets or plates, the spacing of the weldsand the type of metal tused in the sheets or plates without departingfrom the invention. Therefore, the above described applications of themethod should be considered as illustrative only and not as limiting thescope of the claims.

I claim:

l. A method of making a laminated sheet metal structure comprising spotwelding a pair of metal sheets together at spaced apart points, applyinga third sheet of metal to one surface of said pair, applying anelectrode having a relatively extended work-contacting face to theopposite surface of said pair of sheets and an electrode having a smallface to said third sheet, pressing said electrodes tightly against saidsheets, and spot 6 welding said third sheet to the next adjacent sheetonly and at points out of alignment with the welds of the first pair ofsheets.

2. A method of making a laminated sheet metal structure comprising spotwelding a pair of metal sheets, at least one of which is corrugated,together at spaced apart points to form a composite structure havingpassages extending therethrough, placing electrically conductive membersin certain of said passages in electrical contact with said sheets -toeect diffusion of the current passing through said structure to one of apair of welding electrodes positioned in contact with one face of saidcomposite structure, thereafter bringing a third metal sheet intocontact with a surface of said composite structure opposite saidelectrode, applying an electrode to said third sheet, pressing saidelectrodes tightly against said sheets, and spot welding said thirdsheet to the sheet next adjacent thereto only and at points that are inalignment with said members and are also out of alignment with the weldsbetween the rst pair of sheets.

MAURICE PARTIOT.

REFERENCES CITED The iolowing references are of record in the file oi'this patent:

UNITED STATES PATENTS Number Name Date 584,120 Payne et al June 8, 1897952,877 Cowper-Coles Mar. 22, 1910 1,502,437 Poberejsky July 22, 19241,509,384 Walter Sept. 23, 1924 1,842,774 Barnhart Jan. 26, 19321,933,484 Ragsdale Oct. 31, 1933 1,995,368 Sunnen Mar. 28, 19351,995,484 Sullivan Mar. 26, 1935 2,137,909 Hagedorn Nov. 22, 19382,212,481 Sendzimir Aug. 20', 1940 2,233,526 Hagedorn et al Mar. 4, 19412,268,493 OBrien Dec. 30, 1941 2,284,504 Wrighton et al May 26, 19422,304,976 Watter Dec. 15, 1942 2,324,435 Smith July 13, 1943 2,324,808Abbott July 20, 1943 FOREIGN PATENTS Number Country Date 12,984 GreatBritain Oct. 28, 1885 429,459 Great Britain May 30, 1935 459,755 FranceNov. 14, 1913 OTHER REFERENCES Gioliti, Cemen-tation of Iron and Steel,1915, page 333, McGraw-Hill Book Co., New York, N. Y.

Welding Handbook, 1942, page 483, American Welding Society, 33 West 39thStreet New York N. Y.

